Method for cmp uniformity control

ABSTRACT

A method for injecting slurry between the wafer and the pad in chemical mechanical polishing of semiconductor wafers comprising a solid crescent shaped injector the concave trailing edge of which is fitted to the size and shape of leading edge of the polishing head with a gap of between 0 and 3 inches, the bottom surface facing the pad, which rests on the pad with a light load, and through which CMP slurry or components thereof are introduced through one or more openings in the top of the injector and travel through a channel or reservoir the length of the device to the bottom where it or they exit multiple openings in the bottom of the injector, are spread into a thin film, and are introduced at the junction of the surface of the polishing pad and the wafer along the leading edge of the wafer in quantities small enough that all or most of the slurry is introduced between the wafer and the polishing pad, wherein multiple inlets for the introduction of fluids to different points in the channel or directly to the bottom surface of the injector are utilized and some or all of which inlets are fitted with means for controlling the flow of fluid and adjustment is made to the said flow control means during or after polishing to adjust slurry delivery to the wafer surface to improve uniformity of removal rate at the wafer surface.

FIELD OF THE INVENTION

The invention relates to a method for improving slurry use efficiency and polishing removal rate changes in CMP using a slurry injector with multiple variable slurry or other fluid inlets.

BACKGROUND OF THE INVENTION

Chemical Mechanical Polishing (CMP) slurry, together with polishing pads and diamond conditioner disks form the key components of the equipment used to carry out CMP processes in recent years. These polishing pads and diamond conditioner disks have been produced and marketed by several vendors to standards of reliable quality and effectiveness. The function of the slurry is to deliver continuously the mechanical abrasive particles and chemical components to the surface of the wafer and to provide a means of removing reaction products and wafer debris from the polishing surface. There are several varieties of slurry of varying effectiveness and properties known to the art.

At present, for the most common type of CMP tool, the rotary polisher, slurry is applied at a constant flow rate onto the rotating polishing pad using a simple delivery tube, nozzle or spray bar. Fresh slurry flows away from the application point(s) under the influence of gravity and centripetal acceleration and becomes mixed with used slurry or slurry that has passed between the polishing pad and wafer and been involved in polishing.

Old slurry besides being somewhat chemically “spent” additionally contains the debris from wafer, conditioner and pad which if the old slurry re-enters the gap between the wafer and polishing pad are exposed to the wafer surface and can lead to increases in contamination and increases in defectivity. It is therefore important to remove the debris of polishing, and by extension used slurry, from the polishing pad quickly after it is generated and to the greatest extent possible not reintroduce it under the wafer.

Eventually the rotation of the pad brings the slurry into contact with the leading edge of the wafer or the leading edge of a wafer retaining ring, where it forms a bow wave. Some of the fresh slurry at this point is advected into the narrow 10 to 25 micron gap between the wafer and polishing pad and is utilized for polishing. The gap exists because the surface of the pad is rough, the surface of the wafer is relatively smooth and the wafer contacts only the high points of the pad surface. However, most of the fresh slurry remains in the bow wave and is carried to the edge of the pad by the combined rotation of the polishing head and pad. The slurry is then lost over the edge of the pad. Thus, actual slurry utilization, the percentage of new slurry applied that enters the gap between the rough pad surface and the wafer of total slurry applied, is universally quite low in such rotary CMP tools. This is a significant problem because slurry consumption and waste disposal account for a large share of the cost of ownership and operation of a CMP tool.

An additional influence is exerted polishing removal rate from the wafer and uniformity arise because when wafers are polished it is the practice in the art to wash used slurry off of the CMP polishing pad between wafers by application of deionized water to the polishing pad, typically this water is added to the center of the pad. The time between removing one wafer and replacing it with a second is short and invariably a large quantity of water remains on the pad when polishing of the new wafer begins.

This water is not uniformly distributed and as a result it dilutes the newly added slurry in a non-uniform manner causing both a general decrease in removal rate by the diluted slurry and lack of uniformity in removal rate due to variations in slurry concentration on different parts of the pad. Since this effect lasts several seconds it can exert a significant negative effect on anywhere from 25 percent to 50 percent of the time during which the wafer is polished and this in turn can result in a significant and costly reduction in process effectiveness and product quality.

To facilitate the advection or entry of the slurry under the wafer, the practitioners of the prior art have used grooves in the CMP pad. This was effective in making sure that some slurry reached the pad-wafer interface but still allowed most of the slurry to be cast off of the pad without ever having been used. Slurry is expensive and devices, equipment and procedures for providing and removing large amounts of slurry must be included in the CMP process which both complicates and encumbers that process.

Presently there is no effective method available for substantially reducing the amount of slurry used or making sure that most of the slurry introduced to the pad during CMP is actually introduced between the pad and the wafer and utilized as intended before being cast off of the pad. Moreover, there is no effective method available to prevent dilution or contamination of the new slurry applied with water, old slurry or debris from polishing before it is able to enter the gap between the wafer and the pad. And there is currently no way to optimize slurry concentration in different parts of the pad so as to minimize variation of removal rate from the wafer.

Methods to solve these problems to date have, as stated above, consisted of placing grooves in the surface of the CMP pad to conduct some portion of the slurry under the wafer during CMP polishing. In U.S. Pat. No. 5,216,843 (Breivogel et al filing date 24 Sep. 1992) (incorporated herein by reference) “an apparatus for polishing a thin film” . . . “said apparatus comprising” . . . “a pad covering said table, said pad having an upper surface into which have been formed a plurality of preformed grooves, said preformed grooves facilitating the polishing process by creating a corresponding plurality of point contacts at the pad/substrate interface.” and a “means for providing a plurality of micro channel grooves into said upper surface of said pad while polishing said substrate wherein said micro channel grooves aid in facilitating said polishing process by channeling said slurry between said substrate and said pad.” Still in U.S. Pat. No. 7,175,510 (Skyopec et al. filing date 19 Apr. 2005 incorporated herein by reference) a method of polishing wherein “The polishing pad has grooves that channels (sic) slurry between the wafer and polishing pad and rids excess material from the wafer, allowing an efficient polishing of the surface of the wafer.” is described. Even as recently as Skyopec et al, the preferred method for maximizing the amount of slurry that was introduced between the pad and the wafer was preparation of the grooves in the polishing pad surface and the efforts of practitioners of the art were limited to ensuring that these “micro-channels” were regenerated or maintained in a suitable fashion.

In US 2007 0224920 (incorporated herein by reference) these grooves are enhanced by hoes in the pad made in sizes and shapes appropriate to optimise the amount of slurry conducted under the wafer by the grooves. However this does not solve the basic problem of waste of new slurry due to slurry accumulation in the bow wave or the problem of consistent rate of removal polishing.

Moreover, Novellus Systems, Inc. has addressed the slurry utilization problem by means of orbital polishers (U.S. Pat. No. 6,500,055 incorporated herein by reference) in which the slurry is injected through the polishing pad directly under the wafer (U.S. Pat. No. 5,554,064 (incorporated herein by reference). This guarantees high slurry utilization but requires a complex platen and custom pad to accommodate the slurry distribution system and a specialized polishing tool to take advantage of the injection method. Similarly in US 2007 0281592 (incorporated herein by reference) slurries and other conditioning chemicals are introduced and removed through apertures in the diamond conditioning disk for the purpose of facilitating multistep CMP processes but this is not intended to and does not effectively improve the utilization of slurry by directing a larger fraction between the wafer and the CMP pad.

Also in the prior art are U.S. Pat. No. 5,964,413, (incorporated herein by reference) which teaches an Apparatus for dispensing slurry. This is a device for spraying slurry on to the pad rather than pumping it in specific positions at the pad wafer interface and does not provide the desirable benefits sought by the present invention.

In addition, U.S. Pat. No. 6,929,533 (incorporated herein by reference), teaches methods for enhancing within-wafer CMP uniformity. This patent describes methods for enhancing the polish rate uniformity of rotary and linear polishers using slurry dispense bars with multiple nozzles to distribute the slurry over the entire wafer track. The slurry dispenser bars sit above the pad and do not contact it. This method when compared with the present invention lacks the beneficial effect of the creation of a layer of slurry with the same thickness as the wafer-pad gap which is essential in order for significant amounts of the new slurry to be advected under the pad the first time.

U.S. Pat. No. 6,283,840 (incorporated herein by reference) teaches a cleaning and slurry distribution system assembly for use in chemical mechanical polishing apparatus. This apparatus has “an outlet to distribute slurry to the enclosed region to form a reservoir of slurry in the enclosed region, wherein the slurry is distributed to a region not enclosed by the retainer by travelling between the polishing surface and the lower surface of the retainer.” However, the application of the slurry to specific land areas where it is needed is not taught and in fact most slurry is lost through grooves between the land areas which generally exceed the land areas in cross sectional area between the wafer and the polishing pad. This apparatus also fails to teach or accomplish control over flow as a function of radius from the center of the polishing pad and there is no teaching or reported effect of separation of the old spent slurry, dilution water or polishing wastes from the newly applied slurry.

The main function that the apparatus accomplishes is to keep spray from the slurry or from cleaning agents from depositing on the polisher, where the residue can become a source of defect-causing contamination. This is mentioned several times in the description. The background mentions reducing slurry consumption in passing in the last paragraph, but the patent contains no teaching that the apparatus accomplishes this or indeed how it would be accomplished.

U.S. Pat. No. 5,997,392, teaches Slurry injection technique for chemical-mechanical polishing. The slurry application method involves spraying the slurry onto the pad under pressure from a multiplicity of nozzles, however, this invention suffers from the same drawbacks as U.S. Pat. No. 6,929,533 in that lack of precision in the placement and form of the slurry substantially decreases its effectiveness.

“U.S. Pat. No. 4,910,155 (incorporated herein by reference) describes the basic CMP process and utilizes a retaining wall around the polishing pad and polishing table to retain a pool of slurry on the pad. It does not describe a particular method for getting the pooled slurry into the pad wafer gap more effectively. U.S. Pat. No. 5,403,228 (incorporated herein by reference) discloses a technique for mounting multiple polishing pads onto a platen in a CMP process. A seal of material impervious to the chemical action of the polishing slurry is disposed about the perimeter of the interface between the pads and when the pads are assembled the bead squashes and forms a seal and causes the periphery of the upper pad to curve upward creating a bowl-like reservoir for increasing the residence time of slurry on the face of the pad prior to overflowing the pad.

U.S. Pat. No. 3,342,652 (incorporated herein by reference) teaches a process for chemically polishing a semiconductor substrate and a slurry solution is applied to the surface of the pad in bursts as a stream forming a liquid layer between the cloth and the wafers to be polished. The solution is applied from a dispensing bottle and is applied tangentially to the wafer-plate assembly so as to provide maximum washing of the polishing cloth in order to remove waste etching products. U.S. Pat. No. 4,549,374 (incorporated herein by reference) shows the use of a specially formulated abrasive slurry for polishing semiconductor wafers comprising montmorillonite clay in deionized water.”

In U.S. Pat. No. 6,284,092 (incorporated herein by reference), CMP teaches a slurry atomization slurry dispense system in which “ . . . a polishing slurry dispenser device disposed to dispense the slurry toward the pad preferably as a stream or more preferably drops toward the pad surface and a curtain of air to intersect the slurry at or near the polishing pad surface. The wafer is polished using less slurry than a conventional polishing apparatus while still maintaining the polishing rates and polishing uniformity of the prior art polishing apparatus. A preferred dispenser is an elongated housing having a slurry tube and air tube therein each tube having a plurality of spaced apart slurry openings and air openings along its longitudinal axis which tube is preferably positioned radially over at least one-half the diameter of the polishing pad.

A polishing slurry is directed from the slurry tube toward the surface of the pad, preferably in the form of drops, and the air from the air tube forms an air curtain, with the air curtain intersecting the slurry drops preferably at or slightly above the pad surface to atomize the slurry.”

While this system distributes the slurry uniformly it does not do so in a way that insures that the thickness of the slurry layer at the leading edge of the wafer is the thickness of the gap.

U.S. Pat. No. 6,398,627 teaches a slurry dispenser having multiple adjustable nozzles. In the teaching of that art, a “slurry dispensing unit for a chemical mechanical polishing apparatus equipped with multiple slurry dispensing nozzles is disclosed. The slurry dispensing unit is constructed by a dispenser body that has a delivery conduit, a return conduit and a U-shape conduit connected in fluid communication therein between for flowing continuously a slurry solution there through and a plurality of nozzles integrally connected to and in fluid communication with a fluid passageway in the delivery conduit for dispensing a slurry solution. The multiple slurry dispensing nozzles may either have a fixed opening or adjustable openings by utilizing a flow control valve at each nozzle opening. This patent, as with the previous art referred to, possesses no feature that ensures that the thickness of the slurry layer at the leading edge of the wafer is the same as the wafer pad gap.

U.S. Pat. No. 6,429,131 (incorporated herein by reference) concerns CMP cur rate uniformity and teaches improved CMP uniformity achieved by providing improved control of the slurry distribution. Improved slurry distribution is accomplished by, for example, the use of a slurry dispenser that dispenses slurry from a plurality of dispensing points. Providing a squeeze bar between the slurry dispenser and wafer to redistribute the slurry also improves the slurry distribution. This invention can distribute slurry evenly over the pad but does not provide a uniform layer of slurry the thickness of the gap.

Finally in U.S. patent application Ser. No. 12/262,579 (Incorporated herein by reference) a method and device for injecting slurry between the wafer and the polishing pad comprising a solid crescent shaped injector the concave trailing edge of which is fitted to the size and shape of leading edge of the polishing head with a gap of between 0 and 1 inches, which rests on the pad with a light load, the bottom surface facing the pad, and through which CMP slurry or components thereof are introduced through one or more openings in the top of the injector and travel through a channel or reservoir the length of the device to the bottom where it or they exit multiple openings in the bottom of the injector and are, are spread into a thin film, and are introduced at the junction of the surface of the polishing pad and the wafer along the leading edge of the wafer in quantities small enough that all or most of the slurry is introduced between the wafer and the polishing pad. This solves the problem of introducing slurry that is relatively uncontaminated by spent slurry, excessive diluent water or polishing debris into the gap between the wafer and the pad.

Although the creation and maintenance of grooves and micro-channels are essential for the operation of CMP polishing, they still do not afford an efficient means of introduction of slurry between the pad and the wafer whereby most or even a substantial portion of the slurry introduced onto the pad is actually introduced between the pad and the wafer. Furthermore, although a great many methods have been designed for spreading the slurry evenly on the pad none to date have taught a method for preparing a layer of slurry suitably thick for smooth entry into the pad wafer gap. Most of the slurry continues to accumulate in a wave of slurry at the leading edge of the wafer which for the most part moves outward along the leading edge to be dumped off of the edge of the pad and wasted. Moreover, used slurry that has been under the wafer and is contaminated returns as the pad is rotated and mixed with the new slurry at the bow wave decreasing significantly the quality of the slurry used in actual CMP and increasing significantly the waste. And finally none of these methods of the prior art have reduced the negative effects on material removal and uniformity of residual slurry cleaning water added between wafers Furthermore, the one device and method that have been invented to inject slurry into the gap between the wafer and the pad but the aforesaid method as disclosed does not effectively insure even distribution of slurry into the gap between the wafer and the pad. This results in non-uniformity of polishing of the wafer.

SUMMARY OF THE PRESENT INVENTION

The present invention is a method for injecting slurry between the wafer and the pad in chemical mechanical polishing of semiconductor wafers using the apparatus described in U.S. patent application Ser. No. 12/262,579 comprising a solid crescent shaped injector the concave trailing edge of which is fitted to the size and shape of leading edge of the polishing head with a gap of between 0 and 1 inches, the bottom surface facing the pad, which rests on the pad with a light load, and through which CMP slurry or components thereof are introduced through one or more openings in the top of the injector and travel through a channel or reservoir the length of the device to the bottom where it or they exit multiple openings in the bottom of the injector, are spread into a thin film, and are introduced at the junction of the surface of the polishing pad and the wafer along the leading edge of the wafer in quantities small enough that all or most of the slurry is introduced between the wafer and the polishing pad, wherein multiple openings for the introduction of slurry to the device are utilized and fitted with devices that control the flow of slurry of various concentrations or diluent and adjustment is made to these devices during or after polishing to obtain a uniform distribution of new slurry on the land areas of the pad to in turn obtain a more uniform removal rate throughout the wafer.

The invention is more particularly a method for injecting slurry between the wafer and the pad in chemical mechanical polishing of semiconductor wafers in which multiple openings for the introduction of slurry to the device are utilized and fitted with means to control the flow of slurry of various concentrations or diluent or other fluids and adjustment is made to these devices during or after polishing to obtain a uniform distribution of new slurry on the land areas of the pad to in turn obtain a more uniform removal rate throughout the wafer wherein such method of introduction is further combined in a feedback loop with a means of adjusting the devices for flow control so the concentration of the slurry within different parts of the slurry reservoir may be adjusted to improve slurry distribution on the pad.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view from above of the injector.

FIG. 2 is a cross section side view of the injector over the pad.

FIG. 3 is a chart of the feedback system.

FIG. 4 is a graph of the removal rate across the disc in a baseline run with 90 ml/min slurry flow no water.

FIG. 5 is a graph of removal rate with 90 ml/min slurry flow and Needle Valve 3 open at 30 cc/min water flow.

FIG. 6 is a graph of removal rate with 90 ml/min slurry flow and Needle Valves 3, 4 and 5 open at 50 cc/min water flow

DETAILED DESCRIPTION OF THE INVENTION

The inventor of the present invention, seeking to make a more efficient use of slurry in CMP processes and a more efficient method of introduction of slurry between the pad and the wafer that insures that more new slurry is advected under the wafer and the distribution of that slurry is uniform to improve uniformity in polishing of the wafer surface. More particularly the inventor of the present invention has devised a method of adjusting slurry and diluent flow through multiple openings on the top of the injector described in U.S. patent application Ser. No. 12/262,579 so that an even distribution of slurry may be injected onto the pad and even more particularly a sensor and feedback system for measuring the system to determine that distribution of slurry and or polishing are uniform and adjust them quickly and efficiently in the event that they are not.

This apparatus more particularly comprises a solid crescent shaped injector, the concave trailing edge of which conforms to the size and shape of the leading edge of the wafer or polishing head set with a gap of up to 1 inch, which rests on the polishing pad under a light load, the bottom surface facing the polishing pad of which is essentially flat and parallel to the surface of the said polishing pad and in contact with it, and through which CMP slurry, or components thereof, are introduced through multiple tubes attached on one end to the slurry or slurry component source which may be the normal slurry supply system and on the other end to inlets in the top of the injector, and travels through an internal distribution channel or reservoir extending the length of the solid crescent shaped injector and over that part of the polishing pad that is touched by the wafer, through the bottom of the solid crescent shaped injector where the slurry exits multiple openings in the bottom of the solid crescent shaped injector, is spread over the polishing pad surface in a thin film, and is introduced at the junction of the surface of the polishing pad and the wafer along the leading edge of the wafer in quantities small enough to insure that all or most of the slurry is introduced between the wafer and the polishing pad and to the multiple lines on the top of the crescent devices, particularly valves, and more particularly adjustable needle valves, for controlling the flow of slurry or diluent or other fluid to the chamber are affixed and a sensor system, particularly a system that observes slurry concentration on the surface of the pad between the trailing edge of the injector and the leading edge of the wafer.

The method of the present invention has been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available CMP slurry supply systems for CMP tools. Thus, it is an overall objective of the present invention to provide CMP slurry injection methods that remedy the shortcomings of the prior art.

The purpose of this method is to allow more effective injection of slurry into the space between the polishing pad and when and to the extent that that injection is less than optimum, to adjust it to achieve optimum conditions such that slurry use may be optimized at the same time as uniformity of removal rate is improved.

CMP slurry should be fresh (pre-diluted) slurry so that it is more able to wear away and planarize the metal surface of wafers for such semiconductor wafers as silicon wafers or silicon compound wafers that have been plated with copper or tungsten or other materials and thereafter to planarize the semiconductor surface itself. In principle when old slurry or water are allowed to mix with new slurry in large and uncontrolled amounts and much of this mixture is allowed to be disposed of from the polishing pad without ever having been used under the wafer, there is substantial waste of slurry and the slurry that does eventually find its way under the wafer is not entirely effective. Further, uncontrolled dilution of slurry leads to non-uniformity of polishing rates. However, specific controlled dilution of slurry at the injector can result in even flow of slurry so that the amount of slurry entering under each part of the leading edge of the wafer can be made the same or can be otherwise adjusted to suit the needs of the polishing process.

Manufacturers and users of CMP pads need to minimize slurry waste and maximize slurry injection efficiency and consistency in quality of the slurry applied to obtain the most cost effective and high quality polishing of wafers. Additionally manufacturers need to obtain as good a uniformity of removal rate across the wafer as is reasonably possible.

The problem of non-uniformity in surface rate removal for different regions of the wafer in CMP has been known in the art for some time as has the problem of the even flow or distribution of slurry.

The present invention overcomes the problems of the prior art by maintaining the physical separation of used slurry and residual water from newly added slurry on the polishing pad surface by insuring that as much as possible of the new slurry ends up in the gap between the wafer and the polishing pad and not in a bow wave before the leading edge of the wafer where much if not most of it would be sloughed off of the edge of the polishing pad by centripetal forces without ever having been used and by ensuring that slurry is delivered to the wafer in quantities and locations along its leading edge that are conducive to uniform polishing of the wafer surface in addition to which multiple openings for the introduction of slurry to the device are utilized and fitted with means to control the flow of slurry of various concentrations or diluent or other fluids, and adjustment is made to these devices during or after polishing to obtain a uniform distribution of new slurry on the land areas of the polishing pad to in turn obtain a more uniform removal rate throughout the wafer.

Through the use of the slurry injector of the present invention, consistent, effective and reduced volume usage together with suitable allocation of slurry and greater uniformity of removal rate can be achieved easily with together with resulting improved polished wafer quality.

All dimensions for parts in the present invention follow are based on a pad size of about 20″ to 30″ in diameter and a wafer size of between [8″] and [12″] in diameter and may be altered as needed in proportion to changes in the size of the polishing pad and wafer used. The specific dimensions given herein are in no way limiting but are by way of example to demonstrate an effective embodiment of the invention.

The present invention comprises a method for the efficient introduction of slurry between the polishing pad and the wafer that while largely eliminate the waste of slurry characteristic of the CMP polishing methods of the prior art, allow the use of a purer unused and undiluted slurry, in quantities that may be adjusted to be optimally conducive to wafer polishing uniformity, at the polishing pad surface at all times and additionally allow the operator of CMP polishing equipment considerable control over the introduction of slurry between the wafer and the polishing pad.

More particularly, the present invention comprises a method for injecting slurry between the wafer and the polishing pad in the chemical mechanical polishing of semiconductor wafers using the device from U.S. patent application Ser. No. 12/262,579 comprising a solid crescent shaped injector (10) the concave trailing edge (12) of which conforms to the size and shape of leading edge (14) of the wafer (28) with a gap (42) of between 0 and 1 inches, which rests on the polishing pad (26) with a light load, the bottom surface (16) of which is essentially flat and parallel to the surface (36) of the polishing pad (26), and through which CMP slurry or components thereof are introduced through multiple tubes (18) or other suitable means of delivery attached to flow control devices (19) and further to inlets (20) in the top (76) of the solid crescent shaped injector (10) and flow through a channel or reservoir (22) the length of the solid crescent shaped injector (10) to the bottom (78) of said channel or reservoir (22) where it or they exit the solid crescent shaped injector (10) through multiple openings (24) in the bottom (16) thereof and are pressed between the said bottom (16) of the solid crescent shaped injector (10) and the polishing pad (26), spread into a thin film and introduced at the junction of the surface (36) of the polishing pad (26) and the wafer (28) along the leading edge (14) of the wafer (28), preferably on the “land” (30) areas between the grooves (32) in the pad, in quantities small enough and in a film thin enough so that all or most of the slurry is introduced between the wafer (28) and the polishing pad (26) and by which used slurry is more effectively kept separate from newly injected slurry by its concentration in a second bow wave (46) at the leading edge (34) of the solid crescent shaped injector (10).

If multiple inlets (20) for slurry or fluid are used these may all be the same or may differ in size, capacity or configuration. In one embodiment of the present invention, a primary slurry inlet and several other inlets are used. The inlets other than the primary slurry inlet may each carry slurry or they may carry water or other diluent or fluid in any combination or configuration. In one embodiment of the present invention, the primary slurry inlet or inlets introduce slurry to the injector and the remaining inlets introduce water or other diluents or fluids to the injector. In this embodiment the introduction of diluted slurry or water by the said other inlets is preferred and the introduction of water is more preferred. The number of such additional inlets is not particularly limited and in the case where the injector is equipped with a channel the additional inlets (20) may either allow direct introduction of slurry, diluted slurry, water or other diluents directly into the said channel or some or all of such inlets may bypass the channel either in the direction of the leading or trailing edge of the slurry injector (10) and allow introduction of slurry, diluted slurry, water or other diluents directly onto the polishing pad surface. The injector could be equipped with a second parallel distribution channel, however, this would lead to additional complexity rendering adjustment in the application of slurry to the polishing pad more difficult and possibly reducing control over the localized application of particularly low viscosity diluents such as water. In different embodiments of the present invention, all of the inlets may directly enter the channel, all of the inlets may directly supply fluid to the surface of the polishing pad through the bottom surface of the injector or any combination of inlets may be used. Where a channel is used the introduction of at least some of the undiluted slurry is preferred and the introduction of all of the undiluted slurry into the channel is more preferred. In this case, some or all of the diluent may be introduced through inlets directly to polishing pad surface through the bottom surface of the injector. The number of such inlets additional to the first or primary undiluted slurry inlet is not particularly limited but between 1 and 20 inlets is preferred, between 3 and 10 is more preferred and between 5 and 8 is most preferred. Any or all of the inlets (20) may be fitted with flow control devices (19). The means of creating such inlets is not particularly limited and any suitable means may be employed. However, preparing the inlet (20) by drilling through the injector is preferred. The tubes (18) and flow control devices (19) may be attached to the inlet by any suitable means and the use of adhesives or, where appropriate, barbs or bolting are preferred. Where the flow control devices introduce slurry, diluted slurry, water or other diluents directly onto the surface of the polishing pad, the said flow control devices should not protrude from the injector and contact the polishing pad or themselves physically interfere with slurry distribution.

The flow control devices (19) may be attached to power and signal relay cables (not shown) which in turn lead to a data processing center (not shown). Whereas it is possible that all of the flow control devices may be set to maintain the same flow rate for each, it is contemplated by the present invention that flow rates among the inlets (20) may vary individually. A significant and indispensable element of the present invention is the adjustment of flow rates at the inlets (20) using flow control devices (19) to obtain optimum distribution of slurry on the polishing pad, minimizing waste, and at the same time optimizing removal rate. This adjustment may be by adjusting the needle valves after any polishing run and prior to another or they may be carried out during a run. Adjustment may be made by leaving one of the flow control devices (19) entirely or partially open or by leaving more than one of the flow control devices (19) partially or entirely open with the remaining flow control devices (19) closed. Adjustment may entail one some or all of the flow control devices (19) being partially opened and they may all be opened the same amount or partially opened. Adjustment may alter whether any or all of the flow control devices (19) are closed or partially or entirely open and if partially open to what degree. Adjustment may be made between runs or during runs and if during runs may be made within set time limits or continuously.

Additionally a sensor or a sensor array (not shown) may be suspended above the gap and supplied with power and relay cables which lead in turn to the said data processing center (not shown). Slurry, water and other diluents or fluids may be introduced through any of the inlets for the slurry inlet (20) or the flow control devices (19) in any order or configuration without limitation and the composition of the fluids introduced may be constant or vary with time.

As the polishing tool, any suitable rotary polishing tool may be used. In particular, existing rotary polishing tools may be retrofitted with the apparatus of the present invention. Any polishing pad (26) suitable for use in CMP may be used. Moreover, any diamond conditioner disk (not shown) suitable for use in CMP may be used.

For the slurry, any applicable CMP slurry may be used and, for example, silica based and alumina-based slurries may either or both be used.

The solid crescent shaped injector (10) may be constructed of any hard material, such as metal, plastic, ceramic or glass, suitable for CMP processes as a solid block shaped by any suitable means to include the inlets (20) trailing crescent edge (12) and leading crescent edge (34), the openings (24), channels and reservoir (22), where applicable, or in parts to be joined or by layers. Construction by layers (56) of polycarbonate sheeting cut to the appropriate shapes to incorporate the internal channel or reservoir (22) and the leading crescent edge (34) and trailing crescent edge (12) is preferred. This is true both because polycarbonate sheets are cost effective, light and durable and because polycarbonate's transparency allows the operator to see the condition of slurry in the internal channel or reservoir (22) where one is used. Where layers (56) are used, any suitable method including but not limited to adhesives and bolts (80) may be used to hold the layers (56) together and bolts (80) are preferred.

The concave trailing edge (12) of the solid crescent shaped injector (10) is fitted to the size and shape of leading edge (14) of the wafer (28). The trailing edge (12) of the solid crescent shaped injector (10) may be matching in shape and dimension to the leading edge (14) of the wafer (28) or there may be a variation in curve to avoid mechanical interference. A matching edge is preferred, particularly where the gap (42) is small. The length of the crescent shaped injector (10) (difference between the apices of the horns (44)) should be sufficient to substantially cover the leading edge (14) of the wafer (28) or between 4 and 18 inches, depending on the diameter of wafer (28) being polished. Any means of shaping may be used, however, where polycarbonate sheets are used shaping accomplished by cutting is preferred.

The distance between the wafer (28) and the trailing edge (12) of the solid crescent shaped injector (10) at the widest point should be up to 1 inches. The leading edge (14) of the solid crescent shaped injector (10) may be crescent or rectangular in shape or may be any other suitable shape that interferes minimally with CMP process, at the same time allows for sufficient capacity in the slurry channel or reservoir (22) where one is used, and creates a suitable second bow wave (46) to remove the used slurry from the polishing pad (26) before it can mix with the new unused slurry.

The load of the solid crescent shaped injector (10) resting on the polishing pad (26) is between 1 and 10 lb or more and generally is sufficient to apply enough pressure so that the mean gap (42) between the bottom surface (16) of the solid crescent shaped injector (10) and the polishing pad (26) is comparable within a small multiple to the mean gap (42) between the wafer (28) and the pad (26). The latter is frequently measured to be between 10 and 25 microns, but larger or smaller gaps (82) are also possible.

The bottom surface (16) of the solid crescent shaped injector (10) facing the polishing pad (26) is flat and smooth, though depending upon need it may be textured, grooved or shaped. The bottom surface (16) is essentially parallel to the surface (36) of the polishing pad (26). Though in case of need, a variation in pitch or bank could be made. The gap (82) can be adjusted by planarization of the bottom surface (16) of the solid crescent shaped injector (10). The CMP slurry or components thereof are introduced to the solid crescent shaped injector (10) through one or more openings (52) in the top (76) thereof The number and size of openings (24) in the bottom surface (16) are not limited but a diameter of 0.01 to 0.125 inches is preferred and between 40 and 160 openings (24) are preferred. It is preferred that the said openings (24) correspond in position and number to the “land” (30) areas on the polishing pad (36), and one opening (24) placed above each “land” (30) area is more preferred. The linear arrangement of the openings (24) is not limited but it is preferred that they be arranged along a straight or curved line. The openings (24) should be placed at whatever location and separation distance from each other would be suitable for them to be directly above a land (30) on the polishing pad (36).

The means of introducing slurry, water, and other diluents or fluids to the solid crescent shaped injector (10) is not particularly limited but a tube (18) connected to the slurry or water or other diluent supply systems of the CMP tool is preferred. The tube or tubes (18) may be attached to the solid crescent shaped injector (10) by any suitable means but a quick connect coupling (54) is preferred. For the positioning of the primary slurry inlet openings (20) in the top of the solid crescent shaped injector (10), any positioning or pattern may be used but a position coincident with the radius at which a point on the polishing pad (26) has the longest transit time under the wafer (28) is preferred. The flow control device (19) of the present invention is not particularly limited. Any device suitable to control the flow of slurry in a tube including pumps and valves may be used. The use of a needle valve for some or all of the tubes (18) is preferred. The position of the needle valve is not limited and may be at any point on the tubes (18) but affixing the needle valve (19) at the end between the tube (18) and inside the slurry inlet (20) is preferred. The position of the needle valves or other flow control means may be either into the channel or directly through the injector to the polishing pad as described herein. The distribution of the flow control means or needle valves along the injector is not particularly limited bas as stated herein may be evenly spaced or distributed in any pattern and an evenly spaced distribution is preferred. The needle valve may be controlled by any reasonable means and the operator may control them manually or mechanically or mechanically subject to robotic or computer control.

The size of the channel or reservoir (22) and whether it is a narrow channel or a reservoir (22) should be considered when positioning of the inlet or inlets (20).

The solid crescent shaped injector (10) may be made by any suitable means but a method whereby the solid crescent shaped injector (10) is constructed of three layers (56) of shaped or cut hard material, and preferredly three polycarbonate sheets, joined together by any suitable means is preferred. The layers (56) may be of the same or different thickness and any thickness that is not so thin as to result in a solid crescent shaped injector (10) too weak to endure the rigours of CMP polishing or so thick as to be cumbersome and inapplicable may be used and a uniform layer (56) thickness of 0.17 inch for each layer (56) is preferred.

In the event the said layers (56) are used, they may be of uniform thickness or they may be bevelled, particularly the middle layer, if a channel or reservoir (22) is used, to produce a channel or reservoir (22) of varying thickness in the event this is desirable. Layers (56) of uniform thickness are preferred. The lines or channels (22) for introducing slurry to the bottom surface of the injector may be a direct channel through the injector, may be branched or may comprise a channel or reservoir (22) created, in particular, by removing a more extensive section of the middle layer (86) in the three layer case. In the event that such a channel or reservoir (22) is utilized, the shape of the channel or reservoir (22) may be the same essential shape as the solid crescent shaped injector (10) or it may be an oval or ovoid or a simple channel or any other suitable uniform shape. The channel or reservoir (22) should have bleed valves (88) at either end to remove air when slurry is introduced.

A flow meter or other suitable sensors may be added to monitor slurry flow preferably before the point of entry into the solid crescent shape (10).

Where a channel or reservoir (22) is used a reservoir having an essentially oval shape centered on the center of the injector or a channel or reservoir (22) whose lateral boundaries (90) are a fixed distance from the outer lateral boundaries (14) (34) of the solid crescent shaped injector are preferred,

The upper surfaces (60) and lower surfaces (62) of the channel or reservoir (22) may be parallel and flat, may be at a slight planar angle with respect to each other or may be slightly rounded. Parallel, smooth planar upper (60) and lower surfaces (62) of the channel or reservoir (22) are preferred.

The openings (24) by which the slurry exits the solid crescent shaped injector (10) in the bottom surface (16) of the solid crescent shaped injector (10) may be any shape and size but round or oval shapes are preferred and round is more preferred. The diameter of the exit openings (24) may be any diameter but for a total of 68 openings (24) on the solid crescent shaped injector (10) a diameter of about 0.0625 inches is preferred. The openings (24) may be made perpendicular to the bottom surface (16) or at an angle. The openings (24) may be made by any suitable means but drilling is preferred Any positioning and pattern may be used but curvilinear spacing of openings (24) corresponding the radii of the land (30) areas and following the curve of the trailing edge (12) of the solid crescent shaped injector (10) and about ¼ inch ahead of it is preferred.

The flow rate of the slurry through the solid crescent shaped injector (10) is influenced by the location of the inlet or inlets (20) with respect to the radial distance of the said inlet or inlets (20) from the center of the polishing pad (26). Consequently the location of said inlet or inlets (20) as well as the size, shape, angle of incidence, and density pattern of the outlets (24) may be adjusted to optimize flow conditions. The slurry may be introduced into the channel or the reservoir (22) in the solid crescent shaped injector (10) by gravity flow or by pumping. If it is introduced by pumping the rate is not limited but a rate of be approximately 50 ml/min or above for 68 openings (24) or about 0.73 ml/min or above per opening (24) is preferred.

The solid crescent shaped injector (10) position on the polishing pad (26) can be maintained by means of any suitable device but a beam (64) with a rod (66) to which the solid crescent shaped injector (10) is attached is preferred. The beam (64) or rod (66) should be strong enough to withstand the rigors of the CMP process and should be between 0.25 inch and 0.75 inch in diameter or thickness. Stainless steel is preferred as their component material. The solid crescent shaped injector (10) should be detachable from the rod (66) so that it may be cleaned or replaced when worn. This also allows switching of solid crescent shaped injectors (10) with different hole patterns corresponding to different polishing pad (36) groove geometries.

The point of contact between the solid crescent shaped injector (10) and the rod (66) or other means of support in the present invention is gimballed (68) so that the pitch or bank of the solid crescent shaped injector (10) may be adjusted or move slightly. The upper end of the rod (66) may be secured to the support mechanism of the CMP tool by any suitable means such as a set screw (74). A load may be applied using a combination spring (70) and collar (72) with the load being fixed prior to tightening the set screw (74) for the rod (66), or dead weights (50) may arranged on the top surface (76) of the solid crescent shaped injector (10) to apply the load prior to tightening the set screw (74). The collar (72) is fixed to the rod (66) by means of a separate set screw (73). A suitable load sensor may be attached to determine the load during operation.

When slurry, or as the case may be, water or other diluents or fluids, are pumped into the solid crescent shaped injector (10), any suitable flow rate may be used, and for example, slurry or water or other diluents or fluids may be pumped at the rate of 30-300 cc per minute.

The gimbal (68) device at the point of attachment between the solid crescent shaped injector (10) and the rod (66) may be any suitable gimbal (68) device that allows adjustment of the pitch and bank angles without permitting rotation around the axis of the rod (66). This may be a fixed adjustment or the solid crescent shaped injector (10) may be allowed to adjust naturally so that it lies flat against the polishing pad (26) surface (36). This gimbal (68) feature allows the operator to lay down a very thin film of slurry and in so doing also effectively segregate the used slurry in a bow wave (46) at the leading edge of the solid crescent shaped injector (10) without losing the flat orientation of the bottom (16) of the solid crescent shaped injector (10) as it sits on or above the polishing pad (26).

The sensors or sensor array (25) used in the present invention may be any sensor or sensor array capable of observing and reporting accurately the amount of slurry on each land (30) in real time during polishing. Infrared sensors that observe the lower temperatures of newer slurry are preferred.

The method of the present invention may be any method whereby the flow control devices (19) on the tubes (18) may be adjusted to optimize or otherwise manipulate the concentration of slurry on the lands (10) of the pad before the leading edge of the pad (30) so that slurry consumption is optimized and the uniformity of removal rate is maximized. The means of determining the optimization of slurry output and the maximization of uniformity of removal rate are not particularly limited, however, visual inspection and sensor inspection may be used and sensor inspection is preferred for slurry observation and the use of a reflectometer is preferred for measurement of removal rate. The determination of how much to adjust the flow control devices may be made by the operator or it may be automated by a software routine. A software routine is preferred. The actual adjustment is not particularly limited and may be automatic or manual and automatic is preferred.

When polishing is begun and slurry injection is commenced the initial setting of the flow control devices (19) may be based on equal flow rate of diluent through the tubes (18) or some other balance based on experience or calculation. The adjustment of the flow control devices (19) may be sequential or simultaneous or some combination thereof (groups of selected flow control devices adjusted simultaneously for example) and may be continuous, at intervals or after completion of the run and before the next run. By recording the adjustments and response on the data processing unit, a body of data for certain wafers, slurries and conditions may be accumulated.

The precise composition of the diluent of the present invention is not limited, though slurry diluted with water or some other aqueous solution or simply water or some other suitable fluid may be used. It should be observed that where multiple slurry inlets (20) or slurry inlets (20) with additional flow control devices (19) are used, the same slurry at the same concentrations it is normally used in CMP may be applied through multiple slurry inlets (20) or flow control devices (19). The use of such multiple inlets (20) and flow control devices (19) has more than one effect. In addition to allowing the use of diluents potentially altering the viscosity or chemical composition or activity of the slurry, they also serve to allow injection of slurry into parts of the injector that would otherwise be far from the main slurry inlet and this can have a significant impact on slurry flow through different parts of the injector even when no diluent has been used and the concentration of slurry and, consequently, the viscosity, are the same throughout the injector channel. In the alternative, when these additional inlets are placed entirely through the body of the injector, although the motion or concentration of the slurry in the channel itself is no longer affected, the concentration of slurry on the surface of the pad is altered selectively altering in turn the activity of the slurry on the pad and inducing changes in removal rate. In this case, although the amount of slurry passing through different parts of the injector channel is not affected, the concentration of slurry after delivery is. The important thing is that it is possible to control slurry concentration on the pad and thereby the rate of removal. What is desirable about this embodiment is that it allows more precise control over the amount of water, diluted slurry or other diluent contacting a specific area of the pad which allows more specific adjustment of removal rates in some situations.

EXAMPLES

The practice of the present invention is demonstrated without being limited by reference to the following practice examples.

For the following practice examples, a Rohm and Haas IC-10-A2 CMP pad was attached to an Araca Incorporated APD-500 200 mm CMP polishing tool and a Mitsubishi Materials Corporation TRD conditioning disk was attached as well. A stainless steel shaft approximately 6.5 inches in length and 0.3125 inch in diameter was slipped into a hole in an adjustable beam clamped to the support mechanism of the CMP tool. A spring was placed between the collar and the support mechanism along the rod, the spring was compressed, and the collar was attached with a set screw to the rod. This has the effect of transferring the force from the spring to the surface of the pad via the injector. A separate set screw for the rod in the adjustable beam was then used to attach the rod to the support mechanism to fix the load and to prevent the rod from turning about its own axis.

The injector was fabricated with three sheets of clear polycarbonate(GE Plastics XL10, 0.17 inch thickness) cut together using a band saw to produce three identical crescent shapes [FIG. 1] approximately 10 inches from horn to horn and with a trailing edge radius corresponding to a polishing head of diameter 11.125 inches and a width of 1 inch. Four bolt holes were drilled at intervals of about 2 inches on the sides near the convex (leading) edge of the shapes and with a separation of about 4 inches in the middle and in one of these sheets (bottom) the holes were recessed at ⅜ inch diameter to a depth of about 0.1 inch to accept press fit threaded aluminum nuts. A hole ½ inch in diameter was drilled through the other two sheets (top and middle) and half way through the bottom sheet to accept the gimbal mechanism. In the middle sheet a long distribution channel was cut all the way through the length of the sheet to within ¼ inch of the horns at a distance of about ¼ inch equidistant and in front of the concave trailing edge of the middle sheet. The channel was ⅛ inch in width.

Using a separate template constructed with the aid of a polishing pad, 68 holes were drilled ( 1/16 inch diameter) along the course of the channel through the bottom layer at the variable spacing required to align the holes with land areas on the pad. The holes were perpendicular to the surface of the sheets. Finally an inlet hole of ⅜ inch diameter was drilled in the top sheet and fitted with an aluminum inlet tube, a 4 inch section of tubing, and a quick connector suitable for attachment to the tubing used with the polisher. Seven additional holes of 0.089 inches diameter were drilled at even intervals entirely through the slurry injector at positions about ⅛^(th) inch closer to the leading edge of the injector than the leading edge of the channel so that they would bypass and therefore not impede or influence slurry flow through access to the internal channel. The fourth hole was placed at about the midpoint on a curve parallel to the internal channel. The first and seventh holes were placed about a half inch short of the same line parallel to the inner and outer ends of the internal channel. In each of these holes was placed an Airtol model NV-30-3-K needle valve of the same diameter with a barb or lip on the exit side, the part to be inserted, to hold the needle valves fast once inserted. These valves were all shut for the initiation of the practice examples and were opened as indicated in Table 1. When the valves were not closed entirely, they were opened entirely and partially closed valves were not used in these tests.

The sheets were affixed together so that the edges were even with each other and bolted placing the nuts in recesses in the bottom sheet to make the injector. Prior to assembly, gaskets cut from water-resistant fiberglass reinforced double sided adhesive cloth (3M) were attached to the top and bottom of the middle sheet. A gimbal mechanism allowing free adjustment of bank and pitch but not rotation about the axis of the rod was placed in the half inch hole on the top of the injector, secured with a metal pin, and attached to the rod. The slurry delivery tube was attached to the inlet tube of the top sheet, and to the seven needle valves were attached plastic tubing with an external diameter of 0.175 inches and these seven tubes were all connected to a water distribution manifold which in turn was connected to a water supply. The rate of flow of water through these tubes and needle valves was determined by use of a peristalsic pump as the source of deionized water for the water supply manifold. The trailing edge of the injector was adjusted so that it was approximately 0.5 inch from the leading edge of the polishing head, and the position was further adjusted so that the holes on the bottom of the injector lined up with the “land” areas on the pad.

Examples 1-13

After successful preliminary tests of the integrity and stability of the injector using water flow rates between 50 and 200 cc/min and platen rotation rates between 10 and 80 RPM, a polishing test was run as follows: A new Rohm and Haas IC-10-A2 pad was conditioned for one hour using dionized water and a new 3M A165 100 grit conditioning disk on an Araca Incorporated APD-500 polisher using the “best known method” conditioning sweep, which was designed to optimize the flatness of the pad surface over the lifetime of the pad. Two hundred millimeter diameter wafers with a layer of silicon dioxide deposited from a tetraethoxysilane source (known as TEOS wafers) were then polished at 4 PSI for 1 minute with in situ conditioning (conditioning while polishing) using 90 cc/min application of Fujimi PL4072 fumed silica slurry with a platen rotation rate of 55 RPM and a carrier rotation rate of 53 RPM. No rinse was used between wafers.

Prior to polishing wafers to be used for measuring removal rates (“rate wafers”), a used (“dummy”) TEOS wafer was processed for several minutes and then a series of 11 TEOS dummies were polished for one minute each until the mean coefficient of friction (COF) stabilized. A rate wafer was run with no water flow and 90 cc/min slurry flow to provide a baseline and the COF, Shear force Variance, Removal Rate. Absolute Non-uniformity and Percent Non-Uniformity were calculated and reported in Table 1. Mean removal rates measured using a reflectometer from two diameter scans of each of the two rate wafers processed at a flow rate of 30 ml of water per minute through each of the needle valves while the others were shut and at flow rates of 40 ml per minute and 50 ml per minute for valve 2 and at flow rates of 40 ml per minute and 50 ml per minute for valve 4 were recorded and the COF, Shear Force Variance, Absolute non-uniformity and percent non-uniformity were calculated and are reported in Table 1 as examples 1-11. A rate wafer was then again run with no water flow and 90 cc/min slurry flow to provide a baseline and the COF, Shear force Variance, Removal Rate. Absolute Non-uniformity and Percent Non-Uniformity were calculated and reported in Table 1. Then valves 3, 4 and 5 were opened and a total water flow of 50 ml/min was passed through the 3 valves simultaneously (Example 12) and valves 3, 4 and 5 were opened and a total water flow of 75 ml/min was passed through the 3 valves simultaneously (Example 13) and the results were recorded in Table 1.

TABLE 1 cc/mil water & Shear Force Removal Absolute Percent Wafer Example valve number COF Variance (lbf²) Rate A/min NU A NU 1 Baseline  0 0.331 11.41 2525 607 24.08% 2 1 30 valve 1  0.344. 14.85 2178 610 27.99% 3 2 30 valve 2 0.341 15.44 2159 412 19.07% 4 3 30 valve 3 0.340 15.59 2205 475 21.52% 5 4 30 valve 4 0.338 15.11 2245 535 23.84% 6 5 30 valve 5 0.335 12.32 2205 502 22.79% 7 6 30 valve 6 0.334 12.61 2302 670 29.08% 8 7 30 valve 7 0.329 10.96 2374 546 23.11% 9 8 40 valve 2 0.337 16.36 2096 471 22.51% 10 9 50 valve 2 0.340 14.49 2009 501 24.96% 11 10 40 valve 4 0.334 12.85 2162 425 19.72% 12 11 50 valve 4 0.336 12.55 2094 444 21.25% 13 Baseline  0 0.324 8.14 2436 568 23.42% 14 12 50 valves 3 + 4 + 5 0.338 12.09 2002 357 17.79% 15 13 75 valves 3 + 4 + 5 0.341 12.74 1880 327 17.46%

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of the solid crescent slurry injector and the wafer.

10 is the solid crescent shaped injector

12 is the concave trailing edge of the solid crescent shaped injector 10

14 is the wafer

18 is the slurry supply tube

19 are the flow control devices

20 is the slurry inlet in the top of the solid crescent slurry injector 10

21 are the tubing for the flow control devices

22 is the channel or reservoir for conducting slurry in the solid crescent slurry injector 10. It is visible because in this embodiment the body of the solid crescent slurry injector 10 is made of transparent polycarbonate sheets.

23 is the water or slurry or diluent supply manifold.

26 is the polishing pad

28 is the leading edge of the wafer

34 is the leading edge of the solid crescent shaped injector

40 are the bolts holding the solid crescent slurry injector 10 together.

42 is the gap between leading edge 14 of the wafer 26 and trailing edge 12 of the solid crescent slurry injector 10.

44 are the horns at the end of the solid crescent slurry injector 10.

46 is the second bow wave in front of leading edge 34 of the solid crescent slurry injector 10 (Note that the present invention effectively eliminates the first bow wave which would normally form in the gap 42.

54 is the quick connect that connects the tube 18 to the slurry source (not shown).

66 is the rod that holds the solid crescent slurry injector 10

68 is the gimbal attached to the solid crescent slurry injector 10 in which the rod 66 is seated.

FIG. 2 is a side view of the basic unweighted solid crescent slurry injector 10. Numbering not indicated here is the same as in FIG. 1

16 is the bottom surface of the solid crescent slurry injector 10

24 are the openings in the bottom surface 16 of the solid crescent slurry injector 10

30 are the land areas on the upper surface of the polishing pad

32 are the grooves between the land areas 30

36 is the upper surface of the polishing pad 26

52 is an opening for slurry to be admitted to the solid crescent slurry injector 10

56 are the layers from which the solid crescent slurry injector 10 in this embodiment is constructed.

60 is the upper surface of the channel or reservoir 22

62 is the lower surface of the channel or reservoir 22

64 is the beam from the polishing tool (not shown) that supports the injector.

70 is a spring to set load on the entire solid crescent slurry injector 10.

72 is a collar to hold the spring 70 on the rod 66.

73 is a set screw to the collar 72

74 is a set screw to hold the rod 66 to the beam 64

76 is the top surface of the solid crescent slurry injector 10

FIG. 3 is a chart of the feedback system.

FIG. 4 is a graph of the removal rate across the disc in a baseline run with 90 ml/min slurry flow no water made in conjunction with the Examples.

FIG. 5 is a graph of removal rate with 90 ml/min slurry flow and Needle Valve 3 open at 30 cc/min water flow from Example 2.

FIG. 6 is a graph of removal rate with 90 ml/min slurry flow and Needle Valves 3, 4 and 5 open at 50 cc/min water flow from Example 12.

EFFECTS OF THE INVENTION

The present invention is among other things a method for improving the removal rate for CMP of wafers using an injector and multiple inlets for slurry or other fluids, particularly diluents. As the examples show, where seven water valves are added to the standard injector with a single slurry inlet, a substantial change in removal rate as compared to a wafer polished with only slurry introduced into the injector is observed as shown in Table 1 depending upon which valve or valves are opened. Simple alteration of the rate of removal does not tell the operator anything about uniformity however, and this is determined by reflectometer of the disc surface upon completion of polishing. From FIGS. 4, 5 and 6 it is easily observed that by changing the valve configuration, removal rates which are more uniform across the wafer diameter as measured in two perpendicular orientations of the wafer are clearly obtained. Figures for non-uniformity and percent non-uniformity are included in Table 1. By adjustment of the needle valves over a series of polishing tests and reflectometer observations it should be possible to determine the optimum valve settings for a certain slurry introduced at a certain rate and essentially calibrate the injector to provide optimum removal rate performance. This factor together with the inherent reduction of slurry waste and decreased wastage of fresh slurry make the present invention a substantial improvement over the prior art.

Further alterations such as the addition of mechanized feedback loops and greater flexibility in the concentrations and compositions of diluent create additional means of optimizing or improving CMP performance. It should be emphasized that the particular settings that provide optimum performance vary from case to case and are not as important. It is the process for finding them in a particular system that matters and that is one of the elements of the present invention. 

1. A method for injecting slurry between the wafer and the pad in chemical mechanical polishing of semiconductor wafers comprising a solid crescent shaped injector the concave trailing edge of which is fitted to the size and shape of leading edge of the polishing head with a gap of between 0 and 3 inches, the bottom surface facing the pad, which rests on the pad with a light load, and through which CMP slurry or components thereof are introduced through one or more openings in the top of the injector and travel through a channel or reservoir the length of the device to the bottom where it or they exit multiple openings in the bottom of the injector, are spread into a thin film, and are introduced at the junction of the surface of the polishing pad and the wafer along the leading edge of the wafer in quantities small enough that all or most of the slurry is introduced between the wafer and the polishing pad, wherein multiple inlets for the introduction of fluids to different points in the channel and directly through the bottom surface of the injector to the polishing pad are utilized and some or all of which inlets are fitted with means for controlling the flow of fluid and adjustment is made to the said flow control means during or after polishing to adjust slurry delivery to the wafer surface to improve uniformity of removal rate at the wafer surface.
 2. A method according to claim 1 wherein the said number of multiple openings is between 2 and
 10. 3. A method according to claim 1 wherein the at least one of the inlets is for the introduction of slurry to the channel.
 4. A method according to claim 1 wherein all of the inlets introduce slurry, diluted slurry or diluent to the channel.
 5. A method according to claim 1 wherein some inlets introduce slurry, diluted slurry or diluent to the channel and the remaining inlets introduce slurry, diluted slurry or diluent directly to the polishing pad through the bottom surface of the injector.
 6. A method according to claim 1 wherein one or more inlets introduce slurry to the channel and the remainder introduce diluted slurry or other diluent to the polishing pad through the bottom surface of the injector.
 7. A method according to claim 1 wherein said means of controlling the flow of slurry of various concentrations or of diluent is a valve.
 8. A method according to claim 1 wherein the said valve is a needle valve.
 9. A method according to claim 1 wherein all of the inlets are for the introduction of slurry.
 10. A method according to claim 1 wherein the slurry introduced through all of the inlets is of uniform concentration and composition.
 11. A method according to claim 1 wherein different slurries are introduced through different inlets.
 12. A method according to claim 1 wherein the slurry introduced through different inlets is the same slurry but of a different concentration or level of dilution depending upon the inlet.
 13. A method according to claim 11 wherein the slurries introduced through different inlets are of different concentrations or levels of dilution depending upon the inlet.
 14. A method according to claim 12 wherein the slurry is diluted with water.
 15. A method according to claim 13 wherein the slurry is diluted with water.
 16. A method according to claim 1 wherein at least one inlet for slurry is not fitted with a means for controlling flow.
 17. A method according to claim 16 wherein between one and all but one of the inlets, that one inlet being the said slurry inlet, introduce diluent to the said channel.
 18. A method according to claim 16 wherein all of the diluent inlets and all but one of the slurry inlets are fitted with a flow control means.
 19. A method according to claims 11 and 12 wherein the concentration and of slurry or slurries may be varied generally or inlet by inlet over time.
 20. A method according to claim 12 wherein the composition of the slurries may be varied over time.
 21. A method according to claim 1 wherein adjustment of the means of flow control is accomplished mechanically.
 22. A method according to claim 1 wherein adjustment of the means of flow control is accomplished manually.
 23. A method according to claim 1 wherein adjustment of the means of flow control is made during CMP operation according to the results of analysis of data obtained by a sensor or a sensor array indicating the amount or temperature of slurry on the pad surface or removal rate from the wafer surface.
 24. A method according to claim 23 wherein the said sensor or sensor array is an infrared sensor or sensor array to measure the temperature of injected slurry in the gap between the wafer and the injector.
 25. A method according to claim 23 wherein the results are obtained from the sensor or sensor array by visual or audio output.
 26. A method according to claim 23 wherein the sensor data are obtained from the sensor or sensor array by means of an electronic signal.
 27. A method according to claim 23 wherein sensor data are analyzed and indicate that increase or decrease of the flow rate in a particular inlet or inlets will optimize distribution of slurry and consequently the magnitude and uniformity of removal rate.
 28. A method according to claim 23 wherein sensor data analysis feedback is applied manually.
 29. A method according to claim 23 wherein sensor data analysis feedback is mechanical and automatic.
 30. A method according to claim 23 wherein the said means of flow control is a valve and adjustment of the valve is accomplished mechanically in accordance with data processing feedback output based on sensor data.
 31. A method according to claim 23 wherein the said means of flow control is a needle valve and adjustment of the needle valve is accomplished mechanically in accordance with data processing feedback output based on sensor data.
 32. A method according to claim 23 wherein the adjustment of the needle valve is accomplished mechanically by a microstepdown motor.
 33. A method according to claim 22 wherein adjustment of the means of flow control is made for subsequent wafers after determination of the uniformity of removal rate on a wafer or wafers.
 34. A method according to claim 33 wherein uniformity of removal rate is determined by a reflectometer.
 35. A method according to claim 34 wherein the means of flow control is a valve.
 36. The method according to claim 35 wherein the valves are needle valves.
 37. The method according to claim 35 wherein one or more of the inlets are not fitted with needle valves, the inlet or inlets not fitted with a needle valve is for the introduction of slurry and the remainder of the inlets fitted with needle valves are for the introduction of diluent or diluted slurry
 38. The method according to claim 37 wherein one wafer is polished under conditions of the needle valves all being closed except the first needle valve through which diluent or diluted slurry is introduced at a fixed rate, and for each successive wafer polished the needle valve previously used is closed and the next valve opened fully until all needle valves have been run following which, based upon uniformity of removal results of the earlier needle valve configurations subsequent polishing runs involving combinations of completely opened needle valves at suitably adjusted total flow rates followed finally, if necessary, by configurations involving entirely closed, partially open and fully open needle valves to achieve optimum removal rate.
 39. The method according to claim 1 wherein the results of adjustment are measured between polishing runs by reflectometer, there is one slurry inlet set at 90 ml/cm flow rate and 7 water inlets evenly spaced, ⅛ inch from the edge of the leading edge of the channel, in the direction opposite the channel from the wafer, opened all the way through the injector to the bottom surface of the injector, equipped with needle valves, adjustment of the needle valves is manual, and a wafer is polished under conditions of the needle valves all completely closed except for the first needle valve, closest to the center of the polishing pad, through which water is introduced at a 30 ml/min, and for each successive wafer polished, the needle valve previously used is closed and the next valve out from the center of the polishing pad opened fully at the same flow rate until all 7 needle valves have been tested, following which, based upon uniformity of removal rate results of the earlier needle valve configurations, subsequent polishing runs subject to configurations of multiple completely opened needle valve at suitably adjusted total flow rates followed are carried out and, finally, polishing runs subject to needle valve configurations utilizing entirely closed. Partially open and fully open needle valves to achieve optimum removal rate.
 40. The method of claim 1 wherein all of the inlets are evenly spaced.
 41. The method of claim 13 wherein the inlets fitted with flow control means are evenly spaced. 